Air flow or air velocity measurements are useful in many applications. For example, occupational safety standards often require a certain minimum amount of fresh air flow into an occupied building. Such standards can also require accurate means for measuring the air flow to ensure that the minimum fresh air flow is being provided. In addition, heating, ventilation and air conditioning (HVAC) systems often rely on air flow measurements to carry out comfort control operations.
Different air flow measurement schemes have been employed in the past with varying degrees of success. Many of these schemes are used, for example, to measure fresh air flow into a building or facility. Typical schemes involve placing air flow measurement tubes within a long length of ductwork at or near the fresh air inlet of a building. A drawback of these traditional schemes arises from the fact that in many cases, long lengths of ductwork are not available to facilitate proper placement and operation of the air flow measurement tubes.
Accordingly, alternate schemes have been developed to measure air flow without requiring a long duct. One such scheme involves the use of hot wire anemometers. This scheme involves placing a number of temperature measurement devices and heated wires, in or near an air flow inlet. The measured temperature proximate the heated wire is a  function of air flow (convection) as well as current through the wire. Because the current through the wire is controllable and/or measurable, air flow may be estimated using the temperature measurements from areas proximate the wire. While this scheme can be calibrated to produce sufficient accuracy, there is significant cost associated with its use and installation.
Another simpler scheme for measuring the air flow into a building involves the use of a spring-biased door at the air inlet of a building. Inward air flow pushes the door open in varying degrees. The amount that the door is forced open depends on the air flow. As a consequence, a measurement of the position angle of the air inlet door provides a measurement of the inward air flow. While this scheme can represent a more cost effective measurement arrangement than those involve hot wire anemometers, this swinging door arrangement requires extensive calibration as well as complex installation procedures.
Still other air flow measurement schemes suffer other drawbacks. Many include expensive equipment, and others are limited by the amount of air flow they can support.
There is a need, therefore, for an air flow measurement arrangement and/or method that addresses the drawbacks of the prior art. Such an air flow arrangement and/or method preferably balances the need for accuracy with the need for reducing cost and installation complexity.